The present invention relates to an oil pump for an internal combustion engine, and a relief pressure control apparatus for such an oil pump. For example, the oil pump is configured to supply oil to sliding parts and others of the internal combustion engine which is mounted on an automotive vehicle.
International Application Publication WO 2012/100344 A1 discloses a relief pressure control apparatus for an oil pump for an internal combustion engine, wherein the relief pressure control apparatus is configured to control a pump discharge pressure to a suitable level by relief, when the pump discharge pressure becomes excessively high, for example, when the oil pump is operating at high speed. This relief pressure control apparatus includes a relief valve and a pilot valve. The relief valve is configured to control the pump discharge pressure outputted by the oil pump. The pilot valve is configured to control an internal pressure of a back pressure chamber of the relief valve via a directional switching valve, with receipt of the pump discharge pressure as a pilot signal. The relief valve includes: a housing including a valve accommodation chamber; a valve element slidably mounted in the valve accommodation chamber; and a relief spring configured to bias the valve element in one direction. The pilot valve includes: a supply port for supply the introduced pump discharge pressure to the directional switching valve; and a drain port for draining an oil pressure supplied from the directional switching valve to the supply port. The pilot valve is configured to selectively open and close the drain port depending on the oil pressure. The directional switching valve is configured to implement switching between fluid passages in an on-off manner by moving a valve element forward or rearward, to obtain two different levels of relief pressure.